Spatiotemporal Evolution of the Dongting Lake Beach in Recent 90 Years

Using historical topographic maps and aerospace remote sensing data since the 1930s,this study investigates the spatial and temporal evolution of Dongting Lake beach.The evolution characteristics of the beaches in different regions and the related formation mechanism were also analyzed.The results show that Dongting Lake beach expanded from 1622.17 km^(2)in 1938 to 1962.28 km^(2)in 2018.With the addition of 980.96 km^(2)of reclaimed high bay beach,the beach area increased by 1321.07km^(2).However,the change process fluctuated somewhat rather than continuously increased.Substantial expansion of the beach area occurred during 1938-1948 and 1958-1998,while slow contraction of the beach area occurred during 1948-1958 and 1998-2018.Dongting Lake beach was dominated by terrigenous debris,the sedimentary types included lacustrine deposits,river alluvial deposits,floodplain and main channel deposits,and river-lake interaction deposits.The rapid expansion occurred in the estuary delta of the east branch of the Ouchi River,which advanced 38.55 km from the estuary toward the lake over the past 90 years.The causes of the changes in the beach included beach reclamation,sediment changes,and lake sand mining.Seventy embankments(covering 2057.77 km^(2))have been enclosed in the Dongting Lake area since 1930s,of which the high bay beach covered an area of 980.96km^(2).The amount of sediment deposited in Dongting Lake has reached 230857×10^(4) m^(3) since 1950s,which is equivalent to an average deposition height of 0.85 m on the lake's bottom.The mining of lake sand caused the beach to shrink,and the proportion of the beach area decreased from 77.18%in 1998 to 72.60%in 2018.The results of this study provide objective data for protecting the lakeshore's ecosystem and biodiversity and supporting the ecological restoration and environmental protection of the Yangtze River Basin.

Evolution characters of water exchange abilities between Dongting Lake and Yangtze River

By using field-survey hydrological data of the related control stations in Dongting Lake and the Yangtze River mainstream in 1951-2010, the evolution characters of water exchange abilities between the two. water bodies and their response to the operation of the Three Gorges Reservoir （TGR） from different time scales are analyzed based on their hydraulic relations. The results are shown as follows. Firstly, during July-September, the replenishment ability of Three Outlets to Dongting Lake is stronger, and in January-March, the replenishment ability of Dongting Lake to Yangtze River is stronger. Secondly, there has been an obvious inter-decadal wave on the water exchange coefficient between Dongting Lake and Yangtze River. In 1951-1958 and 1959-1968, the replenishment ability of Three Outlets to Dongting Lake was stronger, but in 2003-2010, the replenishment ability of Dongting Lake to Yangtze River has been strengthened. Thirdly, the spill-division ability of Three Outlets weakens, and the water of Dongting Lake coming from Three Outlets decreases either in typical years or under different dispatching modes of the TGR after the operation of the Three Gorges Reservoir. Furthermore, the water of Dongting Lake coming from Four Rivers takes the dominant position, which obviously enhances the replenishment ability of Dongting Lake to Yangtze River. Fourthly, if the effect of the runoff fluctuation in the basin is not considered, the evolution characters of the exchange capacities and the exchange process between Dongting Lake and Yangtze River in different time scales are generally changed with the variation of the water exchange amount between them, although the factors influencing the water exchange capacities between them is very complex. These show that there is an in-line growth or decline relation between the river-lake water exchange ability and the river-lake water exchange amount.

Spatiotemporal distribution and historical evolution of polders in the Dongting Lake area, China

Dongting Lake is the largest lake in the middle reaches of the Yangtze River in China. For centuries, people inhabiting the Dongting Lake area have been reclaiming land and constructing dams for flood resistance, agricultural production, and rural settlement, forming geographical entities known as polders. In this study, the regional spatial distributions of polders in the Dongting Lake area in 1949, 1998, and 2013 were obtained using historical maps and modern remotely sensed data, revealing changes since the establishment of the People's Republic of China. Nanxian County was then selected to demonstrate polder changes at the county level, because it has undergone the most dramatic changes in the area. Different polder change models for the Datonghu, Yule, and Renhe polders were analyzed for eight periods: 1644(the early Qing Dynasty), 1911(the late Qing Dynasty), 1930(the Republic of China), 1949(the People's Republic of China), 1963, 1970, 1998, and 2013. Three resulting polder evolution models are: 1) reclaiming polders from lakes, 2) integrating polders by stream merging, and 3) abandoning polders for flood release. The polder evolution models demonstrate the wisdom of local people in using land resources according to the specific regional conditions. Throughout their long-term historical evolution, the spatial distribution of polders in the Dongting Lake area tended to be homogeneous, and the degree of human disturbance tended to be stable. However, a shift occurred, from pure polder area growth or removal to more comprehensive management and protection of the regional environment.

THE HOLOCENE SEDIMENTAL CHARACTERISTIC AND PALEOCLIMATIC EVOLUTION OF EBINUR LAKE，XINJIANG

On the basis of lacustrine sedimentary profile of Ebinur Lake,sequences of evolution of paleoclimate and paleoenvironment in Ebinur Lake area have been rebuilt by analysing the sedimentary stratigraphy,bio-stratigraphy and gepochemistry as well as the chronological records.The results show that,during the last 10 ha years,the general change trends of the paleoclimate in Ebinur Lake area can be divided into three stages: (1) 10. 2-8.3 ka B. P., a warm-cool dry climate stage;(2) 8.3-3.5 ka B.P.,a warmer moist climate stage (specially,7.3-6. 4 ka B. P.,a relatively stable humid temperate stage);(3) 3. 5 ka B. P.-present, adraught temperate climate stage,similar to the present climate. In addition,there existed clearly several times of secondary undulations of dry-humid climate,i.e. 8.3 ka and 7.3 ka for dry climate

Characteristics of an early Holocene climate and environment from lake sediments in Ebinur region, NW China

The characteristics of climatic environment in the early Holocene epoch were studied through analyzing environmental proxies from the sediments in the Ebinur Lake--a closed one in the arid region. The pollen assemblage and other geochemical indices showed that, the temperature was somewhat low in the period (8.0-11.5 cal kaBP) as a whole, but in the early period (11.5-10.6 cal kaBP) the temperature was higher, in company with more precipitation. In the conversion period from the early Holocene epoch to the middle Holocene epoch (8.9-8.0 cal kaBP) the climate fluctuated remarkably. Particularly the three layers of peat sediment revealed the strong instability of climate in the early Holocene epoch in the Ebinur region. All information on the development of peat and the experimental data of pollen and stable isotopes implied that, the climatic condition at 8.2, 8.6 and 10.5 cal kaBP was characterized by noticeable cold and humidness, and could be regarded as three cold and humid events in the early Holocene epoch.

Environmental evolution and southwest monsoon changes in mid-Holocene recorded by lake sediments in Erhai Lake

IN recent years, much progress has been made in the research of the temporal and spatial changes of East Asian monsoon. To research the environmental evolution and monsoon variations in Holocene in the region of Southwest China, a 310-cm continuous lake sediments core in Erhai Lake, Yunnan Province was sampled with Livingston sampler on July 6, 1996. The lake sediments were separated at 2-cm intervals and the core samples were analyzed with chronology, stable isotope ratios of organic carbon and diatoms determination. Three 14C ages are （4 473±40）a B.P. （98—102 cm）, （5 825±85） a B. P. （144—148 cm） and （7 754±45） a B.P. （198—202 cm）. By 137Cs dating, the sedimentation rate is about 0.3 mm/a and this result is close to the 14C dating results. The average sedimentation rates

基于LMDI模型的土地利用碳排放时空差异及影响因素研究——以洞庭湖区为例

运用碳排放系数法和对数平均迪氏指数(LMDI)模型,对1996—2020年洞庭湖区土地利用变化、土地利用碳排放时空差异及其影响因素进行分析。结果表明:(1)土地利用变化整体呈现出“三增三减”特征,建设用地和未利用地的变化程度较为显著,水域和草地次之,耕地和林地的变化程度最小。(2)总净碳排放量呈不断上升趋势,碳排放高值区由中部转向西、东、南部,土地利用碳足迹压力指数始终大于1,以0.54的年均增幅不断上升。(3)人均GDP、单位GDP用地面积和单位土地碳排放强度是影响土地利用碳排放的主要因子,人均GDP和单位GDP用地面积分别成为促进和减缓洞庭湖区碳排放量增长的主要因素。

近60年洞庭湖水位演变态势研究

辨析洞庭湖历史水位演变态势对保护湖泊生态系统健康运转以及确保长江中下游防洪安全和水资源利用均至关重要。为了定量评估洞庭湖近60年来水位变化特征、程度及规律,基于洞庭湖鹿角、杨柳潭和南咀水文站19612020年逐日水位监测数据,应用Mann-Kendall检验法、小波分析法、累积距平法、滑动t检验法等方法对洞庭湖水位变化趋势性、周期性、突变性进行分析,进而采用IHA-RVA法综合评价洞庭湖突变年前后各站点水位改变度和整体水位改变度。研究结果表明:(1)19612020年,鹿角站和杨柳潭站年均水位呈上升趋势,南咀站年均水位呈下降趋势;3个站点水位周期性变化较为明显,呈现4~5个时间尺度的周期变化规律,第一主周期为55~56年;鹿角站水位突变年份为1979、2003年,杨柳潭站水位突变年份为1978、2003年,南咀站水位突变年份为2003年,综合确定2003年为3个站点突变年份。(2)通过分析突变前后3个站点的水位、时间、频率、延时和改变率5组32个水位指标改变度,发现杨柳潭站水位改变度大于鹿角站和南咀站,鹿角、杨柳潭、南咀站的整体水位改变度分别为43%、48%、42%,均属于中度改变。该研究可为进一步解析洞庭湖水文情势演变规律以及为长江中下游通江湖泊水资源合理利用和水生态环境保护提供参考依据和数据支撑。

安徽巢湖沉积物常量元素特征及其揭示的流域风化强度演变

全新世是人类文明形成发展的重要时期,把握全新世以来气候变化规律将有助于理解全球气候变化,科学应对突发气候事件。通过对安徽巢湖SZK1507孔岩芯沉积物的常量元素含量及其比值特征进行分析,结合AMS^(14)C测年重建了巢湖流域10.8 cal.ka B.P.以来的风化强度演变过程,揭示了流域气候环境变化和可能存在的气候突变事件,并初步探讨了化学风化强度可能的影响因素。结果表明:(1)环境代用指标化学蚀变指数(CIA)、残积系数(Ki)的谷值与风化淋溶系数(Ba)、退碱系数(w)的峰值均出现在砂层和粉砂层,表明砂层和粉砂层的化学风化程度较弱于其他层位。(2)阶段Ⅰ(10.8~9.9 cal.ka B.P.)和阶段Ⅲ(9.3~5.7 cal.ka B.P.)化学风化作用强烈,阶段Ⅱ(9.9~9.3 cal.ka B.P.)化学风化作用弱,阶段Ⅳ(5.7~2.3 cal.ka B.P.)化学风化作用逐渐减弱,阶段Ⅴ(2.3 cal.ka B.P.以来)化学风化作用变化频繁,整体呈减弱特征;此外,化学风化强度与气候变化具有较好的一致性,揭示了全新世以来巢湖流域经历了偏湿→偏干→湿润→湿润转干→变干为主的气候环境演变过程。(3)风化强度变化记录很好地表征出9.3、8.2、4.2和2.8 ka B.P.气候突变事件。通过对巢湖湖相沉积物11000 cal.a B.P.以来的化学蚀变指数、30°N夏季太阳辐射量、神农架三宝洞δ18O记录、神农架大九湖δ^(13)C记录等进行综合对比发现,构造抬升运动提供了稳定的陆源碎屑物质,流域气候环境条件是化学风化强度的控制因素,气候变化背景下的植被演替也影响着风化作用强弱,而粒度主要影响着沉积物化学元素组成。

上游来水来沙与洞庭湖入汇顶托对荆江河段冲淤的影响

三峡工程运用后荆江河段处于持续冲刷状态,分析上游来水来沙与洞庭湖入汇顶托对荆江河段冲淤的影响,对掌握坝下游河道演变规律具有重要意义。本研究基于2003—2020年荆江河段实测水沙及冲淤量资料,建立河段累计冲淤量与河段上下游边界条件之间的函数关系,并重点分析顶托作用对荆江河段冲淤的影响。结果表明:(1)荆江河段累计冲淤量与河段进口水流冲刷强度呈正相关,与进出口水位落差呈负相关,河段冲淤过程是二者共同作用的结果;(2)建立进口水流冲刷强度、进出口水位落差与荆江河段累计冲淤量的函数关系,能较好反映上下游边界条件对河段冲淤过程的影响(R^(2)>0.92);(3) 2003—2020年荆江河段累计冲刷量为12.3亿m^(3),在假设无洞庭湖入汇顶托的情况下比实测值增加0.67亿m^(3),即入汇顶托能使荆江河段冲刷量减少约5%;同期上、下荆江累计冲刷量分别为7.3亿和5.0亿m^(3),入汇顶托能使冲刷量分别减少约1%和16%。洞庭湖入汇顶托会导致荆江河段的冲刷量减少,对下荆江冲淤影响更显著。

基于钻孔记录探究古云梦泽沉积面貌

古云梦泽是晚全新世时期江汉平原与长江最主要的水沙交换载体,其形成演化特征为沉积物所记录,蕴藏了丰富的古环境、古气候信息。为了探讨古云梦泽沉积演化的规律和模式,基于2014~2019年江汉平原野外钻孔采样数据,对江汉平原钻孔沉积物的理化指标包括粒度、总有机碳、磁化率等进行分析,结合加速器质谱碳十四(AMS^(14)C)精准测年和粒度频率曲线得到晚全新世时期江汉平原整体的沉积环境变化序列,进而探讨古云梦泽沉积演化的规律和模式。结果表明:根据钻孔沉积相记录,古云梦泽形成演化过程中出现了“河流-湖泊-三角洲”复合沉积模式;钻孔横向对比发现,三角洲相沉积最先形成于江汉平原西部,并逐渐向东部扩展,表明这种复合沉积模式不仅仅只影响单个钻孔的沉积序列,还在空间上调控了整个古云梦泽的演化。研究成果揭示了历史时期全球变化背景下江汉平原河湖系统自然演变的特征与规律,对于指导江汉湖群的生态恢复和预测未来长江中下游地区江湖关系演变趋势具有重要的意义。

巢湖湖相沉积物元素地球化学揭示的全新世以来水文气候演变

在建立巢湖西岸古湖盆中心SZK1507孔湖相岩芯可靠地层年代序列的基础上,对钻孔地球化学元素进行相关性和主成分分析,发现主成分F1反映了流域侵蚀能力的强弱程度,主成分F2对流域化学淋溶强弱程度反应敏感,主成分F3则指示了湖泊水位的高低,并结合Rb/Sr值环境代用指标重建了区域全新世以来高分辨率水文气候演变。结果表明,水文气候演变过程可以分为7个阶段,阶段Ⅰ(约10.8 cal.ka B.P.—9.9 cal.ka B.P.)、阶段Ⅲ~V(约9.3 cal.ka B.P.—4.2 cal.ka B.P.)气候较为湿润,巢湖水位较高;阶段Ⅱ(约9.9 cal.ka B.P.—9.3 cal.ka B.P.)与阶段VI(约4.2cal.ka B.P.—2.3 cal.ka B.P.)整体上降水减少,湖面收缩,水位降低,气候偏干;阶段VII(约2.3 cal.ka B.P.以来)区域气候波动较大,干湿交替,总体呈现变干的趋势;9.3 cal.ka B.P.、8.2 cal.ka B.P.和4.2 cal.ka B.P.气候突变事件在此沉积记录中也有体现。将巢湖湖相沉积11 cal.ka B.P.以来的Ti元素强度、主成分F1和Rb/Sr值与全新世以来的30°N夏季太阳辐射量、Cariaco盆地Ti含量、ENSO活动指数等进行对比,发现研究区全新世气候突变事件主要受控于北半球夏季太阳辐射、热带辐合带(ITCZ)平均纬度以及厄尔尼诺–南方涛动(ENSO)活动频率等因素。北半球夏季太阳辐射量降低,ITCZ南移,ENSO活动频率增加,夏季风势力减弱,促使了9.3 cal.ka B.P.等干冷事件的发生。研究结果将为理解东亚季风区全新世以来季风和水文气候演变的关系提供可靠依据。

基于多源遥感解译的洞庭湖区自然湖岸线演变过程研究

伴随泥沙淤积、水库运行、湖区围垦、岸线侵占和破坏等自然和人为因素的影响,洞庭湖区湖岸线已发生显著的改变,但是目前仍缺少遥感解译揭示其演变过程。利用1986-2022年多源遥感影像,通过归一化差异植被指数、最大值合成法以及大津法和目视解译相结合的阈值划分方法,识别并提取东洞庭湖、南洞庭湖和目平湖的植被带范围,进而分析洞庭湖区湖岸线的演变规律。通过栅格计算得到湖泊每年(相比于上年)植被带扩张和萎缩的面积,以及1986、1990、2000、2010和2020年植被带变化的空间分布。结果表明,洞庭湖区自然湖岸线呈现普遍扩张的趋势,并且不同位置在不同时期扩张和萎缩面积的占比不尽相同。东洞庭湖、南洞庭湖和目平湖的自然岸线所围水域面积分别缩减144.84、191.42和80.48 km~2,缩减率分别为27.83%、39.20%和48.26%。藕池河东支尾闾汇入东洞庭湖内,通过数字岸线分析系统对其自然岸线进行统计分析,结果表明:藕池河东支尾闾的自然岸线平均每年扩张距离为45 m,净岸线移动最大和最小距离分别为3281和386.93 m,线性回归的决定系数为0.68。总体而言,泥沙冲淤和水位变化是洞庭湖自然岸线变化的主要原因,人类采砂活动在局部区域造成了洞庭湖自然岸线的萎缩。

洞庭湖区旅游产业与生态环境适应性时空演变及影响因素

【目的】诊断旅游产业与生态环境适应性,为旅游产业高质量发展和生态环境可持续承载提供参考依据。【方法】从旅游产业和生态环境2个子系统,压力、状态和响应3个维度构建旅游产业与生态环境适应性评价指标体系,运用熵权Topsis法、适应性评价模型、标准差椭圆及地理探测器,分析洞庭湖区2012—2021年旅游产业与生态环境适应性时空演变及影响因素。【结果】1)旅游产业指数呈现升—降—升变化趋势,生态环境指数呈现波动上升趋势,旅游产业与生态环境适应性指数时空差异显著,呈现中部地区较低、四周地区较高的“盆地型”空间分布格局。2)近10年来适应性时空迁移趋势以东西方向为主导,空间离散程度呈现出先扩大后缩小的变化趋势,重心位于洞庭湖中部地区,集聚特征明显。3)旅游产业与生态环境适应性类型以低度适应为主,县域占比达41.18%,空间格局表现边缘地区>外围地区>中部地区的分布特征。4)旅游资源禀赋、政府调控力度、经济发展水平和环境治理能力是驱动旅游产业与生态环境适应性时空演变的重要因素。【结论】洞庭湖区旅游产业与生态环境适应性较低,县域发展不平衡、不充分问题较突出。未来洞庭湖区旅游产业发展,应立足生态环境承载能力,科学开发旅游资源,加强区域旅游合作,提高旅游产业与生态环境的适应能力。

洞庭湖区生态经济系统时空耦合演变及驱动因素

统筹生态环境与经济发展是促进生态经济可持续发展的内在要求,对推动我国经济高质量发展具有重要的现实意义。本文分别从压力、状态和响应,以及水平、结构和效益3个维度构建生态环境与经济发展评价指标体系,运用耦合协调度模型、探索性空间数据分析法、标准差椭圆和地理探测器等方法,分析洞庭湖区生态经济系统时空耦合演变特征及驱动因素。结果表明:(1)2013—2022年生态经济系统耦合协调度呈现出稳定上升趋势,由0.3798增长到0.6348,空间差异显著,呈现出中部低、四周高的“盆地型”空间分布格局。(2)耦合协调度呈现出显著的正向全局空间自相关,且集聚性不断增强;局部自相关存在低—低和高—高2种集聚类型。耦合协调度的重心位置位于洞庭湖中部地区,并逐渐向西北方向移动。(3)生态弹性、经济发展、科学技术和政府调控是生态经济系统耦合协调度时空演变的主要驱动因素。

基于多源遥感数据的洞庭湖流域时空演变研究

近年来,洞庭湖流域的生态环境面临巨大的压力,主要原因包括自然灾害和人类不合理的开发利用。正确获取流域时空演变趋势对于保护和建设洞庭湖流域的生态环境至关重要。文章基于2017—2021年遥感数据,采用NDWI水体指数阈值法(标准化差异水体指数),分析了洞庭湖在此期间的湖泊流域面积变化趋势,研究了流域重心的迁移趋势,探讨了流域关键问题和脆弱环节。结果表明,大通湖在2017年至2021年3月下旬期间水域变化不大,保持在稳定状态。通江湖泊水域面积变化相对比较大,尤其2019年相比2018年呈断崖式萎缩,由2018年的863 km^(2)萎缩到2019年的648.02 km^(2),减幅214.98 km^(2)。影响湖泊演变的气象因素中,降雨与气温相关性最高。该研究成果可为洞庭湖流域可持续发展的治理措施的制定和科学规划提供重要参考依据。

洞庭湖近30年水环境演变态势及影响因素研究

水量、泥沙和污染物交换作为河流与湖泊之间的关键过程,对湖泊生态环境演变具有复杂而深远的影响.以长江中游典型通江湖泊洞庭湖为研究对象,着眼于"江湖""河湖""人湖"三重作用关系变化,从水文情势、水质、富营养化3个层面剖析了近30年洞庭湖水环境演变态势及主控因素.结果表明:①"江湖"关系变化影响了洞庭湖水沙交换及其年内分配,是湖泊枯水期提前和延长、水沙关系突变等现象的主控因素;"河湖""人湖"关系变化协同加剧了该现象.②"河湖"关系的失衡和"河湖"统筹管理措施缺位,造成入湖河流长期输送大量营养物质,是湖体氮磷污染较重的根源;"江湖""人湖"关系变化协同影响着营养盐分布格局,但影响范围及程度有限.③在"江湖""河湖"作用关系复合影响下,藻类生长条件更为有利,增加了洞庭湖富营养化及水华风险.为保障洞庭湖水环境安全,建议:针对"江湖"作用主导的低枯水位问题,以水资源调控为核心,推进长江与流域上游水库联合生态调度,保障湖泊生态流量;针对"河湖"作用主导的水质恶化问题,以水污染防治为核心,强化流域污染控制,统筹"河湖"一体化监测管理模式,保障湖泊水环境质量;对于"人湖"作用主导的生态破坏问题,以生态空间管控为核心,划定并坚守生态红线,保障生态空间.

全新世以来洞庭湖的演变

本文根据全新世沉积物的岩性、岩相特征和文化遗址的时空分布,结合孢粉资料与历史文献记载,揭示了全新世以来洞庭湖演变的六个阶段:(1)晚更新世末至全新世初为河湖切割平原;(2)中全新世早、中期(8000—5000a B.P.)是湖泊扩展时期;(3)中全新世晚期(5000—3000 a B.P.)四水复合三角洲发育,湖沼洼地零星分布;(4)商周至秦汉(3000—1700 a B.P.)四水分流间洼地湖泊和沼泽广布,汛期河湖水体相连;(5)魏晋至19世纪中叶,洞庭湖逐渐发展至鼎盛阶段;(6)19世纪中叶至今,三角洲迅速推进,湖泊逐渐萎缩。研究认为这种发育演化过程与区域性气候变化、人类活动直接相关。

洞庭湖湖区水质时空演化(1983-2004年)

根据洞庭湖湖区的1983-2004年的水质监测数据,参照GB3838-2002中Ⅲ类水质标准,运用内梅罗水污染指数法进行水质评价,分析了洞庭湖湖区22年来的水质时空变化.结果表明:洞庭湖湖区水质污染在时间上呈有升有降的波动变化.洞庭湖湖区丰水期和洪水期的水质较差,但是从2002年以后,丰水期的水质逐渐好于平水期.污染空间变化表现为入湖河道的污染程度高于湖体,湖体污染呈西洞庭湖的污染较为严重,南洞庭湖其次,东洞庭湖的水质仍较好的格局.

内蒙古高原黄旗海、岱海全新世湖泊演变研究

对内蒙古高原全新世以来黄旗海、岱海湘泊演变过程及其演化规律进行探讨,得出12000—8500a B.P.时湖面回升.但有小的波动;8500—6000a B.P.时为高湖面时期;5000a B.P.前后湖面下降;4000—3500a B.P.时湖面再度上升;3000a B.P.以后湖面急骤收缩,但仍有多次停滞与退缩。造成湖面波动的主要原因与气候变化有关;近期变化还与人类不合理利用有关。